Converting thermal energy into electrical energy is, in general, a process that has long been familiar. The large number of power stations generating electrical energy might be mentioned as an example. Converting thermal energy into kinetic energy is a fundamental part of this process. The kinetic energy is converted, in turn, into electrical energy. In order to run this process and to generate worthwhile quantities of electrical energy in this way, a large quantity of thermal energy is necessary, characterized by a high temperature difference of several hundred degrees Celsius between the materials or objects having the thermal energy and the ambient temperature. Thermal energy at a lower temperature cannot be converted into electrical energy through the processes mentioned above. Thermoelectric processes are known that convert thermal energy at lower temperature levels into electrical energy. It is a feature of thermoelectric processes of this type that they are only able to generate very low voltages or only very small electric currents.
For this reason thermoelectric processes are exploited in instrumentation engineering, where the electrical voltages that are generated and that are, due to the nature of the effects on which they are based, very small, are used as references to a specific temperature or temperature difference. Thermoelectric processes of this type have therefore until now only been used for measuring temperature.
A disadvantage is that in the past it has not been possible to operate electrical equipment, including semiconductor-based electrical equipment, using the power from converters based on thermoelectric effects. This is because the electrical voltages or electrical currents, as mentioned above, are too small.
Until now, no practical and simple solution has been known for the conversion of thermal energy at low temperatures into electrical energy that can in turn be supplied for further use in electrical equipment, rather than merely being used for temperature measurement. Thermal energy at low temperature levels is not used for power conversion as such. This is also due particularly to the fact that thermal energy at low temperature levels is not reliably available in adequate quantities when the electrical power is needed. Thermal energy in the form of waste heat from machines or similar devices may be mentioned as an example of this.